pinctrl/abx500: fix ab9540 alternate function

This fix allows to correctly select default and
alternate pin mode.

By default for all ABx500 family chip, pin default
mode is selected by clearing corresponding bit in
GPIOSELx register except for pins which support
alternate function, in this case, corresponding bit
must be set.

But, due to an unlogical hardware implementation,
for one particular pin (GPIO11) reverse setting
must be done. For that, update the alternate function
array by declaring that this pin supports alternate
function.
Same issue has been fixed in pinctrl-ab8505.c

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>